CHAPTER CHAPTER 2 1 2 Crime-Scene 3 Investigation and 4 5 Evidence Collection 6 LESSONS FROM THE 7 JONBENET RAMSEY CASE The 1996 homicide investiga- which was also part of the crime 8 tion of six-year-old JonBenet scene. Then the victim’s father, Ramsey provides valuable les- John Ramsey, discovered his 9 sons in proper crime-scene daughter’s body in the base- investigation procedures. From ment of the home. He covered this case, we learn how impor- her body with a blanket and 10 tant it is to secure a crime carried her to the living room. In scene. Key forensic evidence doing so, he contaminated the 11 can be lost forever without a crime scene and may have dis- secure crime scene. turbed evidence. That evidence In the Ramsey case, the might have identified the killer. 12 police in Boulder, Colorado, Once the body was found, allowed extensive contamina- family, friends, and police offi- 13 tion of the crime scene. Police ©AP Photo/Paul Sakuma cers remained close by. The first thought JonBenet had The Ramsey Home in Boulder, Colorado. Ramseys and visitors were 14 been kidnapped because of allowed to move freely around a ransom note found by her the house. One friend even mother. For this reason, the police did not search helped clean the kitchen, wiping down the 15 the house until seven hours after the family counters with a spray cleaner—possibly wiping called 911. The first-responding police officer away evidence. Many hours passed before police 16 was investigating the report of the kidnapping. blocked off the basement room. A pathologist The officer did not think to open the basement did not examine the body until more than 18 door, and so did not discover the murdered body hours after the crime took place. 17 of the girl. Officers at this crime scene obviously made Believing the crime was a kidnapping, the serious mistakes that may have resulted in the police blocked off JonBenet’s bedroom with contamination or destruction of evidence. To this yellow and black crime-scene tape to preserve day, the crime remains unsolved. Go to the Gale evidence her kidnapper may have left behind. Forensic Sciences eCollection for more informa- But they did not seal off the rest of the house, tion on this case. 20 31559_02_ch02_p020-047.indd 20 10/2/10 1:57:0 Objectives By the end of this chapter you will be able to: 2.1 Summarize Locard’s exchange principle. 2.2 Identify four examples of trace evidence. 2.3 Distinguish between direct and circumstantial evidence. 2.4 Identify the type of professionals who are present at a crime scene. 2.5 Summarize the seven steps of a crime-scene investigation. 2.6 Explain the importance of securing the crime scene. 2.7 Identify the methods by which a crime scene is documented. 2.8 Demonstrate proper technique in collecting and packaging trace evidence. 2.9 Describe how evidence from a crime scene is analyzed. direct evidence evidence that (if Vocabulary true) proves an alleged fact, chain of custody the documented and such as an eyewitness account unbroken transfer of evidence of a crime circumstantial evidence (indirect fi rst responder the first police evidence) evidence used to officer to arrive at a crime imply a fact but not prove it scene directly individual evidence a kind of class evidence material that evidence that identifies a connects an individual or particular person or thing thing to a certain group (see paper bindle a folded paper used individual evidence) to hold trace evidence crime-scene investigation a primary crime scene the location multidisciplinary approach in where the crime took place which scientific and legal professionals work together secondary crime scene a location to solve a crime other than the primary crime scene, but that is in some way crime-scene reconstruction a related to the crime, where hypothesis of the sequence of evidence is found events from before the crime was committed through its trace evidence small but commission measurable amounts of physical or biological material found at a crime scene 10/2/10 1:57:46 31559_02_ch02_p020-047.indd 21 CHAPTER INTRODUCTION How is it possible to identify the person who committed a crime? A single hair or clothing fiber can allow a crime to be reconstructed and lead police 1 to the responsible person. The goal of a crime-scene investigation is to rec- ognize, document, and collect evidence at the scene of a crime. Solving the 2 crime will then depend on piecing together the evidence to form a picture of what happened at the crime scene. 3 Obj. 2.1 and 2.2 PRINCIPLE OF EXCHANGE 4 Whenever two people come into contact with each other, a physical transfer 5 occurs. Hair, skin cells, clothing fibers, pollen, glass fragments, debris from a person’s clothing, makeup, or any number of different types of material 6 can be transferred from one person to another. To a forensic examiner, these transferred materials constitute what is called trace evidence. Some 7 common examples of trace evidence include: • Pet hair on your clothes or rugs 8 • Hair on your brush • Fingerprints on a glass 9 • Soil tracked into your house on your shoes • A drop of blood on a T-shirt 10 • A used facial tissue 11 • Paint chips • Broken glass 12 • A fiber from clothing The first person to note this condition was Dr. Edmond Locard, direc- 13 tor of the world’s first forensic laboratory in Lyon, France. He established several important ideas that are still a part of forensic studies today. Locard’s 14 exchange principle states that when a person comes into contact with an object or another person, a cross-transfer of physical evidence can occur. The exchanged materials indicate that the two objects were in contact. Trace 15 evidence can be found on both persons (and/or objects) because of this cross-transfer. This evidence that is exchanged bears a silent witness to the 16 criminal act. Locard used transfer (trace) evidence from under a female victim’s fingernails to help identify her attacker. 17 The second part of Locard’s principle states that the intensity, duration, and nature of the materials in contact determine the extent of the transfer. More transfer would be noted if two individuals engaged in a fistfight than if a person simply brushed past another person. 22 Crime-Scene Investigation and Evidence Collection 31559_02_ch02_p020-047.indd 22 10/2/10 1:58:1 TYPES OF EVIDENCE Obj. 2.3 Evidence can be classified into two types: direct evidence and circumstantial evidence (Figure 2-1). Direct evidence includes firsthand observations such as eyewitness accounts or police dashboard video cameras. For example, a Figure 2-1. Classification of witness states that she saw a defendant pointing a gun at a victim during a types of evidence. robbery. In court, direct evidence involves testimony by a witness about what that witness personally saw, heard, or did. Confessions are also considered Evidence direct evidence. Circumstantial evidence is indirect evidence that can be used to imply a Direct Circumstantial fact but that does not directly prove it. No one, other than the suspect and victim, actually sees when circumstantial evidence is left at the crime scene. But circumstantial evidence found at a crime scene may provide a link Physical Biological between a crime scene and a suspect. For example, finding a suspect’s gun at the site of a shooting is circumstantial evidence of the suspect’s presence there. Circumstantial evidence can be either physical or biological in nature. Physical evidence includes impressions such as fingerprints, footprints, shoe prints, tire impressions, and tool marks. Physical evidence also includes fibers, weapons, bullets, and shell casings. Biological evidence includes body fluids, hair, plant parts, and natural fibers. Most physical evidence, with the exception of fingerprints, reduces the number of suspects to a specific, smaller group of individuals. Biological evidence may make the group of suspects very small, or reduce it to a likely individual, which is more persuasive in court. Trace evidence is a type of circumstantial evidence, examples of which include hair found on a brush, fingerprints on a glass, blood drops on a shirt, soil tracked into a house from shoes, and others (Figure 2-2). Evidence can also be divided into class evidence and individual evidence. Class evidence narrows an identity to a group of persons or things. Knowing It is relatively easy to the ABO blood type of a sample of blood from a crime scene tells us that recover DNA from ciga- one of many persons with that blood type may have been there. It also rette ends found at the allows us to exclude anyone with a different blood type. Individual evidence scene of a crime. narrows an identity to a single person or thing. Individual evidence typically has such a unique combination of characteristics that it could only belong to one person or thing, such as a fingerprint. Figure 2-2. Common examples of trace evidence. Animal or human hair Fingerprints Soil or plant material (pollen) Body fluids such as mucus, semen, saliva, or blood Fiber or debris from clothing Paint chips, broken glass, or chemicals such as drugs or explosives Crime-Scene Investigation and Evidence Collection 23 31559_02_ch02_p020-047.indd 23 10/2/10 1:58:4 CHAPTER Obj. 2.4 THE CRIME-SCENE INVESTIGATION TEAM 1 Who is involved in a crime-scene investigation? The team is made up of legal and scientific professionals who work together to solve a crime.